Add timeout command support for macOS (#108)

* feat(timeout): add cross-platform timeout support for macOS

Add portable timeout wrapper that automatically detects and uses the
appropriate timeout command based on the platform:
- Linux: Uses standard GNU `timeout` from coreutils
- macOS: Uses `gtimeout` from Homebrew coreutils

Changes:
- Add lib/timeout_utils.sh with detect_timeout_command() and
  portable_timeout() functions
- Update ralph_loop.sh to source timeout_utils.sh and use
  portable_timeout for Claude Code execution
- Update install.sh to check for coreutils on macOS and provide
  installation instructions
- Update test mocks to include gtimeout and portable_timeout
- Update README.md with macOS coreutils installation instructions
- Update CLAUDE.md with timeout_utils.sh documentation

Users on macOS now need to install coreutils: brew install coreutils

* Update model reference in opencode-review workflow

* Update model name in opencode-review workflow

* Update model version in opencode-review workflow

* Update model version in opencode-review workflow

* Update lib/timeout_utils.sh

Co-authored-by: macroscopeapp[bot] <170038800+macroscopeapp[bot]@users.noreply.github.com>

* Update opencode-review.yml

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: macroscopeapp[bot] <170038800+macroscopeapp[bot]@users.noreply.github.com>

CLAUDE.md

@@ -52,6 +52,13 @@ The system uses a modular architecture with reusable components in the `lib/` di
    - ISO timestamp generation for logging
    - Epoch time calculations for rate limiting
 
+4. **lib/timeout_utils.sh** - Cross-platform timeout command utilities
+   - Detects and uses appropriate timeout command for the platform
+   - Linux: Uses standard `timeout` from GNU coreutils
+   - macOS: Uses `gtimeout` from Homebrew coreutils
+   - `portable_timeout()` function for seamless cross-platform execution
+   - Automatic detection with caching for performance
+
 ## Key Commands
 
 ### Installation